Recovering picric acid from washwater.



H! A. GARDNER,

or wasnmc'ron, nrsrarc'r or corra.

EECOVEBING PICBIC ACID FROM WASHWATER.

l l t m Drawing.

To all whom it may concern:

Be it known that I, HENRY A. GARDNER, a

citizen of the United States, residing at Washington, District of Columbia, have invented a new and useful Improvement in Recovering Picric Acid from Washwater, of which the following is description.

The object of my invention is to recover picric acid from wash water containing picric acid in solution. In the manufacture of picric acid, the crystals are washed with water to remove the impurities incident to the recess of manufacture. Picric acid goes into solution. in the Wash water to the" extent of about 1 per cent. at ordinary room temperatures. The loss thus occasioned is ofttimes very great to the producer; cially when prclon ed washing with large amounts of water is necessary. Moreover,

such wash water is intensely yellow in color and cannot be disposed of in the same mannor as most industrial liquors.

' In order that the %rocess may be ractised by those skilled in t e art I shall escribe a preferred way of carrying it out, it being understood that the detailed procedure vneed not be followed so long asthe essential steps recited in the claims are adhered to.

To 100 pounds (12 gallons) of the wash water there are added 20 pounds of sodium as niter ca e, refer-ably bisulfate NaHSOQ lmown commercially condition. '1. e liquid ma be stirred until the bisulfate dissolves. A liquor of approximately 17 Baum (1130-1140 sp. gr.)-results. At this strength, practically all of the icric. acid is thrownout occulent condition, 'rising to the surface of the heavy liquor.

Specification of Letters Eatent.

a full, clear, and exact in a finely divided of solution m a' Patented am a, rear.

Application filed December 16, 1915. Serial Ito. 37,275.

The picric tion. To the wash water liquor which is now very light in color, may be added a very small quantity, say from 1 to 5 per cent. of a bleaching powder, preferably oxychlorid of lime. The liquor which contains the free sulfuric acid present in the NaHSO, causes liberation of chlorin in suficient quantity to bleach any slight traces of picric ac'd present; The liquor is stirred until ecolorized. The purpose of this step is merely to destroy the slight yellow color of the water so that it may, without objection, be disposed of in the ordinar way.

Having now in ly described my invention, what I claim and desire to protect by Letters Patent is- 1. The process of recovering picric acid from wash water which to the wash water sodium ibisulfate, in such amount as to form a high gravity solution in which the picric acid is substantially insoluble and from which the picric acid is thrown out in a flocculent form. that floats to the surface, thereby facilitating its removal.

2. The process of recovering picric acid from wash water cont the same which consists in adding to the wash water sodium bisulfate, thereby throwing the picric acid out of solution, removing the picric acid, and

adding bleaching powder to the wash water to liberate chlorin decolorize the liquid.

In testimony of which invention, hereunto set my order to thoroughly I have consists in adding acid is now removed by filtrahand, at Philadelphia, on this 11th day of December, 1915. 

